1. Field of the Invention
This invention relates to a method for producing a pyridine derivative which is an important intermediate in the field of medicines, agricultural chemicals, catalytic ligands, combinatorial chemistry, organic electroluminescence elements, charge transport materials, electron transport materials, electrophotographic photo-sensitive materials, dyes, liquid crystals and the like.
2. Description of the Related Art
Methods for producing pyridine ring using an acetyl compound as the material have been developed in recent years. For example, a method has been disclosed in which pyridine ring is constructed under a relatively mild condition with a high yield using a vinamidinium compound obtained by carrying out Vilsmeier reaction of a carboxylic acid derivative (cf. International Publication No. 99/55830 and JP-A-2001-261653, “J. Org. Chem., 4571-4574 (2000)”, “J. Org. Chem., 8415-8420 (2000)” and “J. Org. Chem., 4194-4199 (2001)”. However, this method has two technical problems. One of them is that since dimethylamine, which is volatile and exerts a serious influence upon environment is generated in a large amount, a special gas collector is required for preventing release of this into the air. Also, the other problem is the high cost, because it is difficult to isolate such a vinamidinium compound as a chloride salt, thus resulting in a low yield as a rule (cf. “Chem. Mater., 676 (1996)”, “Collect. Czech. Chem. Commun., 3051 (1961)” and “Collect. Czech. Chem. Commun., 2125 (1965)”. As a method for solving this problem, a method in which a vinamidinium compound of hexafluorophosphoric acid (PF6) salt is isolated has been disclosed. However, since hexafluorophosphoric acid (PF6) ion severely corrodes glass, a general purpose rector made of glass cannot be used, there is a problem in that a special cost is required for the treatment of waste water containing fluorine ion.
As a method, which does not use an ionic precursor, a method is also known in which pyridine ring is constructed by an aminoacrolein derivative (cf. abovementioned “J. Org. Chem., 4571-4574 (2000)”, “J. Org. Chem., 8415-8420 (2000)” and “J. Org. Chem., 4194-4199 (2001)”). However, this method also has a problem in that dimethylamine is generated by the reaction.
On the other hand, as a method for synthesizing a pyrimidinium salt, a method is known in which it is synthesized from a malonaldehyde compound or a vinamidinium compound and a urea derivative (cf. “J. Chem. Soc. Perkin Trans. 1, 1862-1869 (1977)” and “Liebigs Ann. Chem., 1368-1379 (1986)”. However, synthesis from a vinamidinium compound cannot avoid the problem of causing corrosion and bad smell, but rather results in the increase of cost because the number of processes is increased, so that a more inexpensive production method has been in demand.